The general goal of this research is to examine developmental influences on social behaviors and the neuroendocrine mechanisms of these influences. Using as a model the prairie vole, we have observed that apparently minor changes in the manner in which families are "manipulated" in early life can have life-long consequences. We propose to study the relationship between early experiences, including the influence of parental stimulation, and the later tendency to show social behaviors including alloparental behavior, the capacity to form a partner preference, the tendency to show same-sex aggression (possibly indicative of mate guarding), as well as reactivity to stressors. We also propose to test the hypothesis that the behavioral changes we have observed reflect modifications in neuropeptides, including central and blood levels of arginine vasopressin (AVP), oxytocin (OT) or corticotropin releasing hormone (CRH), and the steroid hormone, corticosterone (CORT). Receptor autoradiography will be used to examine the effects of early experience on later regional receptor binding for the OT, AVP (Via), and CRH (type 1 and 2). Intergenerational effects of these experiences will be examined as well.